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1 // Copyright 2006-2008 the V8 project authors. All rights reserved. | 1 // Copyright 2006-2008 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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150 template<class T, int shift, int size> | 150 template<class T, int shift, int size> |
151 class BitField { | 151 class BitField { |
152 public: | 152 public: |
153 // Tells whether the provided value fits into the bit field. | 153 // Tells whether the provided value fits into the bit field. |
154 static bool is_valid(T value) { | 154 static bool is_valid(T value) { |
155 return (static_cast<uint32_t>(value) & ~((1U << (size)) - 1)) == 0; | 155 return (static_cast<uint32_t>(value) & ~((1U << (size)) - 1)) == 0; |
156 } | 156 } |
157 | 157 |
158 // Returns a uint32_t mask of bit field. | 158 // Returns a uint32_t mask of bit field. |
159 static uint32_t mask() { | 159 static uint32_t mask() { |
160 return (1U << (size + shift)) - (1U << shift); | 160 // To use all bits of a uint32 in a bitfield without compiler warnings we |
| 161 // have to compute 2^32 without using a shift count of 32. |
| 162 return ((1U << shift) << size) - (1U << shift); |
161 } | 163 } |
162 | 164 |
163 // Returns a uint32_t with the bit field value encoded. | 165 // Returns a uint32_t with the bit field value encoded. |
164 static uint32_t encode(T value) { | 166 static uint32_t encode(T value) { |
165 ASSERT(is_valid(value)); | 167 ASSERT(is_valid(value)); |
166 return static_cast<uint32_t>(value) << shift; | 168 return static_cast<uint32_t>(value) << shift; |
167 } | 169 } |
168 | 170 |
169 // Extracts the bit field from the value. | 171 // Extracts the bit field from the value. |
170 static T decode(uint32_t value) { | 172 static T decode(uint32_t value) { |
171 return static_cast<T>((value >> shift) & ((1U << (size)) - 1)); | 173 return static_cast<T>((value & mask()) >> shift); |
172 } | 174 } |
173 }; | 175 }; |
174 | 176 |
175 | 177 |
176 // ---------------------------------------------------------------------------- | 178 // ---------------------------------------------------------------------------- |
177 // Support for compressed, machine-independent encoding | 179 // Support for compressed, machine-independent encoding |
178 // and decoding of integer values of arbitrary size. | 180 // and decoding of integer values of arbitrary size. |
179 | 181 |
180 // Encoding and decoding from/to a buffer at position p; | 182 // Encoding and decoding from/to a buffer at position p; |
181 // the result is the position after the encoded integer. | 183 // the result is the position after the encoded integer. |
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583 } | 585 } |
584 } | 586 } |
585 | 587 |
586 | 588 |
587 // Calculate 10^exponent. | 589 // Calculate 10^exponent. |
588 int TenToThe(int exponent); | 590 int TenToThe(int exponent); |
589 | 591 |
590 } } // namespace v8::internal | 592 } } // namespace v8::internal |
591 | 593 |
592 #endif // V8_UTILS_H_ | 594 #endif // V8_UTILS_H_ |
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